getting the MH msg number

[Douglas N. Arnold]

Is their a resource that would allow me to access the MH message number
for a mail message when constructing the LITEMPLATE resource string?  I
didn't find one in the documentation, but it seems a natural thing.
I want to include the message number on the main index page.

(Every message in an MH mail folder has a message number which is a
positive integer and which coincides with the name of the file storing
the message.  The message numbers of messages in a mail folder need not
be consecutive.)